Compressor unloader



@ch 8, H46" 5. R. HIRSCH 2,403,932

COMPRESSOR UNLOADER I Filed May 17. 1944 2 Sheet-Sheet 1 LEAKAGE F77 girl/Um at R. Kirsch.

Patented Oct. 8, 1946 COMPRESSOR UN'LOADER Sylvan Roos Hirsch, Utica, N. Y., assignor to Brunner Manufacturing Company, Utica, N. Y., a corporation of New York Application May 17, 1944, Serial No. 536,007

8 Claims.

This invention relates to a refrigeration compressor and aims to provide a novel means whereby differential pressure is relieved from the discharge side to the suction side across the piston or pistons to enable the'motor to start against practically no load.

A prime object is to provide means for unloading the compressor which employs a release or bleeder valve in combination with an external tube or the equivalent situated in the path of the air stream from the usual condenser fan so that the tube will be slightly cooled to cause a minute condensation of oil entrained in the gas stream, which condensed oil is collected in such positions as to cover and seal said release or bleeder valve to positively prevent communication between the discharge pressure and the compressor suction pressure which would impair the capacity of the apparatus.

Another important aim is to efiect the mounting of the necessary check valve in the head of the compressor and to utilize the removable valve plate which houses and supports the normal operating valves of the compressor, as a support and seat for the check valve.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims, and the several views illustrated in the accompanying drawings.

In said drawings:

Figure l is a substantially central longitudinal sectional view through a hermetic compressor embodying the present invention, and

Figure 2 is a vertical sectiona1 view through said hermetic compressor taken at a right angle to Figure 1.

In said drawings, the compressor generally designated It], may be of the usual two cylinder construction having a housing I I with which a, housing I2 is cast integrally about an electric motor l3 having a main rotatable shaft l4 suitably ,iournaled in bearings at I5 and IQ of the housings ID and II. The crankcase of the compressor is in communication with the base of the motor housing at an opening I"! or otherwise, so that lubricating oil l8 for the working parts will flow from one to the other.

The drive or operating shaft for the compressor at E9 is a continuation or part of the shaft l4 and it is equipped with eccentrics at 20 in operative relation to straps or pitmans 2| connected by wrist pins 22 to pistons 23 operable in cylinders 24 formed in the housing I l.

A head 25 is detachably bolted at 26 to the housing H and the bolts 26 removably secure between the housing and head, a plate 21 for conventional or usual suction and discharge valves 28 and 29 controlling the entrance and passage of gas to and from the cylinders 24 through ports 39 and 3 I, respectively.

.The gas passage is generally designated 32 and may consist of an L-shaped portion 33 in the compressor housing at the suction side, a gas stream portion 34 of L-shape at the discharge side, ports 35 and 36 in communication therewith, respectively, through the valve plate 21, a portion 31 in the head 25 in communication with ports 30 and 35, and a portion 38 in said head 25 in, communication with said ports 3| and 36. The hermetic compressor, as best shown in Figure 2, discharges refrigerant gas, usually Freon-12, through a conduit 39 into a condenser 48 where the refrigerant gas is liquified so as to collect in a receiver 4! from' which it travels through the conduit to an expansion valve 42, thence into an evaporator 43, where the liquid is vaporized or converted to a gas, and it then returns to the suction side of the compressor to the portion 33 of the gas passageway 32.

During the operation of the refrigeration system, the pressures in the condenser 40 will be around one hundred and twenty-five to one hundred and fifty pounds while the pressures in the evaporator 43 will be anywhere from a vacuum to perhaps fifty pounds, depending on the temperature desired in the evaporator. When the proper amount of cooling is developed and no further temperature reduction in the evaporator 43 is necessary, the compressor will shutdown by the action of a usual refrigeration control (not shown) and it does so with a pressure difference across the pistons 23 of approximately one hundred and fifty pounds at the discharge side to fifty pounds 0n the suction side. This differ ential constitutes a very heavy strain against the motor l3 upon again starting, requiring a comparatively high amount of torque or efiort to attain the end. The present invention relieves the cylinders of such load and hence the motor can start against practically no load, and promptly.

The aforesaid valve mountin late 21 also mounts a check valve 44, the same having. a reduced stem 45 passing through the port 36 and also having a pin 48 passing therethrough and engageable with the upper surface of plate 21 to suspend such check valve. The latter has a disk like head 46 at its lower end located in the passageway portion 34 and coacting with a valve seat 41 embedded in the plate 21. This check valve 44 has an upper or plunger like head 49 at the upper end of stem 45 and such head 49 has a leakage fit in a chamber or passage 50. From the passage 50, leads a release line or cOoling coil which is external so as to be in the path of air from the fan of the condenser (not shown), and which line or conduit 5| is connected to discharge into the motor housing I2 and from the same into the crankcase of the compressor.

Said conduit 5| discharges direct into a well or chamber 52 provided in a block or plate 53 fastened to the motor housing |2. The latter has a port therethrough in communication with the chamber or well 52 which is adapted to be closed when the compressor is running by a release or bleeder valve 55 in the form of a metallic leaf or blade so as to be flexible and which is fastened to the housing |2 by means of a screw or the like at 56. A seat 51 for said valve 55 is embedded in the housing l2 around the port 54.

Fixed on one end of the shaft |4 so as to rotate with the latter is a centrifugal governor means to actuate the valve 55 to control the opening and closing of the bleeder port 54. This mechanism is generally designated 58 and comprises a cup 53 suitably fastened to the shaft 14 provided with a central bore 60 for a slidable plunger 6| having a finger 62 of less diameter than the port 54 and disposed therein. An expansive coil spring 63 located in the bore 65 urges projection of the plunger 6! to such an extent that it deflects and opens the valve 55 when the motor and compressor are not running.

Generally L-shaped governor arms 54 are pivoted at 65 to lugs 66 on the cup 55. Any desired number of the governor arms may be employed and it will be noted that at one end, they abut the plunger 6| and at the other ends have Weights 65'. During operation of the motor and compressor, the governor arms 64 act centrifugally to throw the weighted ends 65' outwardly and throw the other ends inwardly, thereby retracting the plunger BI and maintaining the finger 62 retracted and out of engagement with the valve 55 which remains closed due to its inherent flexibility.

During operation, because of the characteristics of the refrigerant used, for instance Freon- 12, there is a flow of entrained oil with the Freon gas at all times. This is advantageous inasmuch as the oil which leaves on the discharge of the compressor returns from evaporato 43, enters the portion 33 of the passageway 52 and the excess oil drains from the gas stream back into the housing II and its crankcase through a port 51 of such housing. It will be appreciated that the crankcase and motor housing are at suction pressure, whereas chamber 50 and conduit 5| are at discharge pressure. This makes it imperative that the release valve 55 be sealed tightly; otherwise the gas will by-pass into conduit 5| rather than continuing into the condenser 40.

When the compressor end is running, the governor arms 64 through centrifugal action are thrown outwardly and since their inner ends bear against the plunger 6|, the bleeder valve 55 will seat or close. At the beginning of operation, the oil laden gas at discharge pressure, will leak past the plunger like head 49 of the check valve 44 into chamber or passage 59 and conduit 5| and thence into the chamber or well 52, hold- 7 ing the bleeder valve 55 against its seat. Such gas being saturated with oil vapor and due to cooling in the conduit 5|, condenses and oil collects in the well or chamber 52. Within a matter of seconds it completely fills such well or chamber because the latter is made relatively small to facilitate immediate flooding. This oil seals the bleeder valve 55 effectively and absolutely so that no leakage can occur. When the motor l3 stops, the governor arms 64 collapse and under the action of spring 63, finger 62 pushes forward, moving bleeder valve 55 off of its seat and thereupon all liquid and vapor from the well or chamber 52 bleeds through the port 54 into the housing l2 and crankcase where suction pressure prevails. The drop in pressure in chamber 59 provides a differential force across the upper part of the check valve 44 or head 49 which causes it to rise and seat itself against seat 41 at the disk 45. The discharge pressure in the part 34 of the passageway acts against the disk 45 causing'it to seal itself tightly against said seat 41. The leak fit between head 49 and chamber 53 permits all discharged gas from the compressor head to be released into the crankcase through the bleeder conduit 5| and release or bleeder valve 55. Because of the action traced, the pistons 23 and cylinders 24 have only suction pressure against which they must act upon restarting and this gives complete unloading of the machine. Upon restarting, the discharge spaces are filled with discharged gas which balances the pressure from the condenser 40 and causes the check valve 44 to drop by gravity, thereby opening up the passage for the gas from the pistons 23 to the condenser 40.

While one form of the invention has been shown for purposes of illustration, it is to be clearly understood that various changes in the details of construction and arrangement of parts may be made without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In a refrigeration compressor, a head having a chamber provided with a port in communication with the gas passage of the compressor, conduit means in communication with said chamber and with the crankcase of the compressor to convey oil-laden gas from the chamber to the crankcase when the compressor is idle and for con- 50 densation of the oil in the conduit means when the compressor is operating, a check valve arranged to close said port through differential pressures on opposite sides thereof, said check valve having a leakage fit at the entrance of said 55 conduit means, and a bleeder valve controlling the communication of the conduit means to the crankcase positioned so as to be sealed by the aforesaid condensation of the oil in said conduit means when the compressor is operating.

2. In a refrigeration compressor, a head having a chamber provided with a port in communication with the gas passage of the compressor, conduit means in communication with said chamber and with the crankcase of the compressor to con- 65 vey oil-laden gas from the chamber to the crankcase when the compressor is idle and for condensation of the oil in the conduit means when the compressor is operating, a check valve arranged to close said port through difierential pressures 70 on opposite sides thereof, said check valve having a leakage fit at the entrance of said conduit means, and a bleeder valve controlling the communication of the conduit means to the crankcase positioned so as to be sealed by the aforesaid condensation of the oil in said conduit means when the compressor is operating, means to open the bleeder valve, and centrifugal mechanism operable by the compressor to retract the last mentioned means during operation of the compressor so that the bleeder valve will remain closed during operation of the compressor.

3. In a refrigeration compressor, a conduit means in communication with the gas passage of the compressor and with the crankcase of the latter to convey oil-laden gas from the passage to the crankcase when the compressor is idle and for condensation of the oil in the conduit means when the compressor is operating, a check valve controlling the passage of the oil-laden gas from the passage to the conduit, and a bleeder valve controlling the communication of the conduit means to the crankcase positioned so as to be sealed by the aforesaid condensation of the oil in said conduit means when the compressor is operating.

4. In a refrigeration compressor, a conduit externally thereof in communication with the gas passage of the compressor and with the crankcase of the latter to convey oil-laden gas from the passage to the crankcase when the compressor is idle, said conduit being disposed in the path of air circulated by the fan of the condenser of the compressor so as to condense oil in the conduit, a check valve controlling the passage of the oil-laden gas from the passage to the conduit, said check valve having a leakage fit at the entrance to the conduit, and a bleeder valve controlling the communication of the conduit to the crankcase positioned so as to be sealed by the aforesaid condensation of the oil in said conduit when the compressor is operating.

5. In a refrigeration compressor, a head having a chamber provided with a port in communication with the gas passage of the compressor, conduit means in communication with said chamber and with the crankcase of the compressor to convey oil-laden gas from the chamber to the crankcase when the compressor is idle and for condensation of the oil in the conduit means when the compressor is operating, a check valve arranged to close said port through differential pressures on opposite sides thereof, said check valve having a leakage fit at the entrance of said conduit means, a bleeder valve controlling the communication of the conduit means to the crankcase positioned so as to be sealed by condensed oil in said conduit means when the compressor is operating, said conduit means being externally of the compressor and including a well in which said bleeder valve is located and which collects the aforesaid condensation of the oil in sealing engagement with the bleeder valve, the wall of the compressor having a passage therethrough adapted to be closed by said valve and through which condensed oil returns to the crankcase, a plunger having a part movable in the last mentioned passage, means urging the plunger to a position to normally open said bleeder valve, and centrifugal means operable by the compressor to maintain 6 said plunger retracted duringoperation so that the bleeder valve will remain closed.

6. In a refrigerant compressor having a plate between its housing and head mounting inlet and outlet valve means for the piston and cylinder mechanism of the compressor,'said head having a chamber provided with a port in communication with the gas passage of the compressor, a check valve located in said port having a head and a piston, conduit means in communication with said chamber and with the crankcase of the compressor to convey oil-laden gas from the chamber to the crankcase when the compressor is idle and for condensation of the oil in the conduit means when the compressor is operating, said check valve being operable through differential pressures in said passage and chamber, said piston having a leakage fit at the entrance to said conduit means and said head being arranged to close said port, a bleeder valve controlling the communication of the conduit means to the crankcase, said conduit means having a Well to collect condensed oil about the valve to seal the same when the compressor is operating, means urging the valve to open position when the compressor is idle, and centrifugal means operable by the compressor to retract the last mentioned means.

'7. In a refrigerant compressor, a conduit means leading from the head thereof and disposed in communication with the gas passage of the compressor and with the crankcase of the latter to convey oil-laden gas from the passage to the crankcase when the compressor is idle and for condensation of the oil in the conduit means when the compressor is operating, a check Valve controlling the passage of the oil-laden gas from the passage to the conduit, and a bleeder valve controlling the communication of the conduit means to the crankcase positioned so as to be sealed by the aforesaid condensation of oil in said conduit means when the compressor is operating.

8. In a refrigeration compressor, a head having a chamber provided with a port in communication with the gas passage of the compressor, conduit means in communication with said chamber and with the crankcase of the compressor to convey oil-laden gas from the chamber to the crankcase when the compressor is idle and for condensation of the oil in the conduit means when the compressor is operating, a check valve arranged to close said port through differential pressures on opposite sides thereof, said check valve having a leakage fit at the entrance of said conduit means, a bleeder valve controlling the communication of the conduit means to the crankcase positioned so as to be sealed by the aforesaid condensation of the oil in said conduit means when the compressor is operating, the compressor having a plate located between its head and housing mounting the valves for the piston and cylinder mechanism of the compressor, said check valve also being mounted by said head.

SYLVAN ROOS HIRSCH. 

